Electronics: 3 transistor discrete preamp with good performance
Updated 2026This discrete class A preamp is based on the information in this Zetex datasheet.
A PCB layout (the full Diptrace project) for this is available and can be downloaded below.
It would be quite trivial to construct this on veroboard (as I did with my prototypes) but the PCB layout provided makes for a neater job.
This little preamp has excellent performance and very low noise. I have compared this to several commercial designs including Cambridge C500, Rotel RC971, Adcom GFP345 and it compared very favourably.
See the gallery images below for performance measurements, the schematic and layout details.
The full DipTrace project (including the schematic and PCB layout) can be downloaded here.
Q3 (output transistor) dissipates around 260mW (collector current is ~18mA) - I would recommend fitting a TO92 heat sink to Q3 to ensure it remains cool.
Click here to see RMAA test results
Arta and REW tests results below:
